Now that Geometry Nodes is here Should I still learn Animation Nodes?
It depends on your use case.  I still use Animation Nodes due to the fact that I can use it with loops and include python scripts with it, which makes it very powerful.
The original creator of Animation Nodes is also one of the developers working on Geometry nodes  (Jacques Lucke).
I have no doubt geometry nodes will eventually get there but it will take time, the thing is how long are you willing to wait.
Geometry Nodes Project Link: